Monthly Archives: September 2017

9/29/2017 – Open source is open source

This has come up again, and when people start yelling about others, it gets me a little angry.  Think of this blog post as another one of those where I’m just complaining.  It is only tangentially related to pinball, but it irks me so here we go.

I’m a big proponent of open source.  Why?  Because open source tools have enabled me to create a bunch of great things.  Things that would not have been possible without open source.  Let’s go over the tools that I use most days in my life:  gcc, linux, python, eclipse,  and millions of others.  That list doesn’t include many subprojects like kicad, gimp, audacity, etc.  That fails to mention open standards such as c, c++, IP, UDP which makes our world go around.  I guess that I’m not just talking about open source, but transparency and open standards.

Everything that I have produced for the Open Pinball Project (OPP) is under the GPLv3 license.   Why is that license important to me, and why not simply release the stuff as un-copyrighted?  An un-copyrighted work can be used by everyone (That’s good).  Here is the important distinction.  If you base your project off a GPLv3 project, it also most be released into the public domain.  This is referred to as copyleft.  Anything that is derived from the original GPLv3 copyrighted material must also be available for others derive further works.

So anyone can take anything in the OPP repository and use it for their own purposes.  The only stipulation that I really care about, is that if they do that, and make improvements, those improvements most also be available publicly so others can easily get the improvements and new works.  That ends up helping to increase the quality of the software or hardware in the future.

So why did I release it with that particular license?  OPP is months of hard work.  Maybe even years.  I have no idea how much time I have spent on it over the last 10 or 15 years.  I want others to be able to leverage my work so that they can learn from it, extend it, and generally use anything that they find useful.

I take copyrights very seriously.  Here is a strange fact that most people don’t know.  If you use the OPP pinball framework, sound can be either place in the sounds folder, or the sounds/copyright subfolder.  If it is in the copyright subfolder, it should not be saved to the repository and should simply exist on the physical machine.  For the Van Halen pinball machine, there are many Van Halen/Hagar songs that are played in the background.  That’s all copyrighted material, so I don’t have the rights to put that in the repository.  If the framework can’t find the sound file, and it is supposed to be in the copyrighted folder, it plays a standard sound clip stating “that is copyrighted”.

At one point a few years back, people were complaining that others were using their work in ways that it wasn’t meant.  I believe MPF (mission pinball framework) was originally branched from PROC work that Gerry, Mike, and some others did.  I think this was in regards to MPF supporting multiple pieces of hardware.  Don’t complain about that.  Feel honored that your hard work is getting new life and others are benefiting from using it.  That is the point of open source.  It allows others to use your sweat and tears and make something better than what you ever imagined.

People aren’t “stealing” your work…they are extending it.  Imitation is the highest form of flattery.  If you don’t want others to use your work, don’t release it as open source software/hardware/whatever.  Keep it closed and locked away, and I really do feel that your stuff will suffer when an open source solution comes along.  The reason that so many people use the PROC platform is because it is relatively open, and it has a well defined interface.  It has a skeleton framework that others can use to create their own projects.

So why did I get on this rant?  Strangely it is because of Ben Heck.  Ben Heck and Mike from HomePin are having a little tiff.  The PinHeck system I believe was released under the Creative Commons – Share Alike (CC-SA) license.  (That holds many of the same copyleft attributes as GPLv3).  It seems that Mike, or people working for Mike, may have based some of his designs on the PinHeck system.

So a couple quick points.  Under that license you must attribute the original design in some way.  Yada, yada, this is based on such and such.  Regardless of the license, that is the right thing to do.  If that is what happened, just fess up Mike and say it.  There is nothing illegal and lock stock and barrel copying that design and using it for your own purpose because it was released under CC-SA.  Any fixes that he made to the design, he must publish them because it is a copyleft license.

So, I assume when Ben caught wind of this, he pulled the files from the server.  I haven’t looked lately if they are there.  The CC-SA license is irrevocable.  You can’t simply say, sorry, I now don’t want it to be open to the public.  Once open source, it is always open source.  The legal ramifications would be impossible to reconcile since others by design could have based their works on your work.

Pulling things off the server is absurd.  Once on the internet, it is always on the internet.  There is a project called the internet archive that lets you go back in time and find things that people have posted on the internet and then removed.  Even though Ben has removed the content, it is still out there.  I have all the design/art files that Ben posted for America’s Most Haunted (AMH).  They were put out there so others could extend his work and make mods and toppers.  They could even build another AMH if they wanted to spend the time.  They are still readily available on the internet archive.

So that gets me to the last point.  Ben mentioned Charlie caught wind of someone trying to build another AMH.  Maybe it was me, maybe it was somebody else.  The truth is I actually considered it.  Charlie, Ben, you can rest assured, that I have no desire to make an AMH from scratch.  That being said, it would be a technically interesting project, but I don’t feel it is worth the time or effort.

I’m still hoping for somebody to create a completely open source pinball machine from scratch.  Maybe in the next 10 years.

If anybody has more details on the origins of MPF, why Ben pulled the art files, etc, that is more correct, I will be happy to fix the above post or post corrections.  Most of this is third or forth hand information that I’ve gleaned from the internet so it is not very reliable.

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9/21/2017 – Updated NeoPixel Library

This is the first step in a multi step process to update how NeoPixels are dealt with in the OPP framework.  This is going to be pretty techy centric, so I apologize in advance.  (Truth be told, I really have no idea who reads this blog, so maybe those two people like techy topics.  I just don’t know).

The original implementation of lighting NeoPixels using the PSoC used a SPI bus to create the protocol.  A single bit sent to a NeoPixel is a waveform which is high for 417ns, low or high depending on if the bit is 1 or 0 for the next 417ns, and low for the last 417ns.  If you add these 3 portions of the waveform together, a single bit takes 1.25 us to send.  The SPI bus is one of the simplest buses.  To send a 1, it sends a high for a clock cycle.  To send a 0, it sends a low for a clock cycle.  If I set the clock of the SPI so a full clock cycle is 417ns, I can have the hardware send a bit stream at the correct rate.  There is one problem.  Instead of sending a single bit, I have to send the framing portion of the protocol, so I end up sending 1×0.  (If I want to send a 1, I send 110.  If I want to send a 0, I send 100.  Simple).  Here’s the problem.  Making 3 bits out of 1 bit kind of stinks because it keeps crossing byte boundaries and such.  Really quite annoying.

One way to reduce this annoyance is to just store everything as 3 bits in RAM.  That means that each Neopixel requires 9 bytes (24 bits/Neopixel * 3 = 72 bits or 9 bytes).  As mentioned in the last post, the PSoC 4200 only has 4K of RAM, so that disappears pretty fast.

Another way is to generate the framing on the fly.  So every time that a bit is sent to a NeoPixel it is pre-pended with a 1 and post-pended with a 0.  This takes much more processing time, but saves RAM.  (This was the original implementation, and the code that contains all the bit shifts and boundary checking is magnificent.  Completely unreadable).

Neither of these solutions are optimal.  (Heck, they all really kind of stink).  Enter the little PLD that is part of the PSoC 4200.  Why not create a little state machine to pull bytes from a FIFO and create the framing in hardware.  That way, the processor doesn’t have to do any of the bit banging stuff.  As an added bonus, the PSoC has internal FIFOs that can be set for either 24 bits (RGB Neopixels) or 32 bits (RGBW Neopixels).  In that way, the processor just has to keep the FIFO from under-flowing and can use a single write to send a complete NeoPixel update value.  Very clean.

At this point, I’ve created a library that does all the NeoPixel heavy lifting with the state machine included and an interrupt to keep the FIFO from under-flowing.  In the OPP code, I will simply pre-allocate 3 bytes for every NeoPixel in memory, then as MPF or whatever framework wants to update the value of a NeoPixel, it just has to send the index, and the new value.  At this point I’ve just finished the library, and with the previous NeoPixel incarnation, I had already set up commands to change NeoPixel values.  I might update those commands to be less restrictive.

Using this library, the load on the processor should be as small as possible using the PSoC4.  Only thing that would be better is to buy a PSoC5 and set up a DMA to fill the FIFO.  That would mean the updates could happen without any processor intervention at all except for starting the DMA.

Here is a link to the Cypress question, and the final library solution that I posted.  Since I’m going to integrate it into the OPP firmware, there is probably little reason to click this link, but it does have the library.  Cypress Developer Community Link